1. Field of the Invention
The present invention relates to a device for detecting a position and an intensity of light. The invention can detect irradiating direction, height, intensity, insolation of sun beam, for example, utilizing the photoconducting effect of amorphous silicon type semiconductor and so forth. The present invention is particularly, but not limitatively, applicable for an air conditioner system for an automotive vehicle to detect intensity of insolation with high precision for providing data for the calculation of insolation dependent thermal load.
2. Description of the Related Art
Such technology has been proposed in Japanese Unexamined Patent Publication (Kokai) No. 59-328116 for "Photo Potentiometer" and Japanese Unexamined Patent Publication No. 63-164281 for "Position Detecting Device". The former publication proposes a position detecting device (photo potentiometer) employing a photoconductive film that lowers its resistance value when light is irradiated thereon. The later publication discloses a position detecting device that comprises a conductive layer including a amorphous semiconductor layer with a p-i-n junction, a transparent conductive layer and a metal.
In the former position detecting device employing the photoconductive film, a leak current is caused at a portion not irradiated by a light beam due to thermal excitation of electrons at elevated temperatures, as shown in FIG. 35. The leak current can offset an output voltage from a component potential value corresponding to a light irradiating position (position of a light spot H) to make an accurate measurement of the position difficult.
On the other hand, in the case of the later position detecting device employing the amorphous semiconductor layer, the following problems can be encountered. A light current detected by irradiation of the light beam normally has a small magnitude, e.g. 100 nA. This requires a high sensitivity amplifier for subsequent arithmetic processes. As a result, the device becomes large and expensive.
The present invention solves the problems set forth above. Therefore, it is an object of the present invention to provide a device for detecting a position and an intensity of a light which has a large magnitude of output voltage corresponding to irradiation of a light beam (high sensitivity), can provide stable detecting accuracy for a minimized leak current even at an elevated temperature, and can provide a signal indicative of an irradiating direction, the height of a light as well as intensity of the light.